This disclosure relates to bacterial diagnostics, and more particularly to methods and compositions for detecting antibiotic resistant bacteria using preferred primers, probes, and assays directed to genes encoding extended spectrum beta-lactamase.
β-Lactam antibiotics (beta-lactam antibiotics) are a broad class of antibiotics, consisting of all antibiotic agents that contain a β-lactam ring in their molecular structures. This includes penicillin derivatives (penams), cephalosporins (cephems), monobactams and carbapenems. (Holten K B 2000). Most β-lactam antibiotics work by inhibiting cell wall biosynthesis in the bacterial organism and are the most widely used group of antibiotics. β-Lactam antibiotics are indicated for the prophylaxis and treatment of bacterial infections caused by susceptible organisms. At first, β-lactam antibiotics were mainly active only against Gram-positive bacteria, yet the recently developed broad-spectrum β-lactam antibiotics are active against various Gram-negative organisms, which has increased their usefulness.
The production of β-lactamases is the predominant cause of resistance to β-lactam antibiotics in gram-negative bacteria. The CTX-M beta-lactamases enzymes were named for their greater activity against cefotaxime. Evolution of multidrug resistant (MDR) bacteria under the pressure of excessive antibiotic use with horizontal gene transfer provide the means by which genes such as bla(CTX-M) spread amongst different bacterial species and strains (Hawkey P M 2009, Liebana et al. 2013). More than 80 CTX-M enzymes are currently known. CTX-M1-, and CTX-M9-groups represent five and nine closely related enzymes, respectively, and are particularly clinically relevant (Garrido et al. 2014; Helldal et al. 2013; Onnberg et al. 2011; Dallenne et al. 2010). CTX-M enzymes are observed in different members of the family Enterobacteriaceae which include, among others, Salmonella and E. coli. Typically the blaCTX-M gene is located on transferable plasmids of different sizes and structures, with the group 1 and 9, respectively, 97 and 98% similar (Bonnet 2004). The specific detection of clinical relevant groups 1 and 9 in the background of less clinical relevant CTX-M groups present special challenges.
There exists a clinical need for the rapid detection of the carriers of antibiotic resistant β-lactamase genes among which the CTX-M1 and CTX-M9 groups have higher clinical prevalence rates.